The invention relates to a process for heating the intake air in internal-combustion engines by means of a flame starting system.
A process of this type is known from German Patent Specification 3,342,865. This is concerned with a flame starting system, in which the air flowing through the intake pipe is preheated in the warming-up phase of the internal-combustion engine to prevent so-called "white smoke". For this purpose, in the suction pipe of the internal-combustion engine there is provided a combustion chamber in which a fuel-injection nozzle and a heater plug are arranged. For starting the internal-combustion engine at relatively low temperatures, the heater plug is preheated, and after the expiry of the preheating time, during the starting of the engine, fuel is delivered via a solenoid valve to the fuel-injection nozzle and consequently into the combustion chamber of the flame starting system. The fuel ignited in the combustion chamber preheats the intake air flowing past and allows a reliable ignition of the cylinders of the internal-combustion engine at low outside temperatures. A continuous current is fed to the heater plug for the duration of a specific first period of time until the engine is turning over reliably, and, after the expiry of this first period of time, a pulsed current corresponding to reduced power is fed to it for a second period of time until the engine has reached a specific operating temperature.
A disadvantage here is that a fixed preheating time, during which the heater plug is supplied with voltage, is assumed for the preheating, and consequently the preheating temperature of the heater plug necessary for starting is not always safely reached.
An object of the invention is to provide a process, starting from the state of the art, by means of which the preheating temperature of the heater plug necessary for starting is safely reached independently of changing boundary conditions.
This object is achieved according to the invention by an arrangement wherein the following cyclically repeating steps are carried out:
(a) detection of the voltage available at the output of the control unit, PA1 (b) determination of a preheating time (T.sub.v), associated with this voltage value, for the heater plug, PA1 (c) determination on of a step value (.DELTA.S) from the division of a predetermined standard value (S) for the preheating time by the value determined for the preheating time (T.sub.v), PA1 (d) summing of the individual step values (.DELTA.S) in a memory erased at the commencement of the process, and PA1 (e) comparison of the memory content with the predetermined standard value (S) and termination of the preheating when the standard value (S) is reached, or return to process step (a) as long as the standard value (S) is not reached.
During the operation of preheating the heater plug, the voltage available at the output of the control unit is detected continuously and an associated preheating time is determined from the voltage values. A predetermined standardized value for the preheating time is divided by the necessary preheating time determined and is filed in a previously erased memory. This operation is repeated according to a fixed chronological cycle, the result is added to the value filed in the memory and the sum is compared with the predetermined standard value. This operation is repeated until the standard value is reached. When the standard value is reached, the preheating time of the flame starting system is terminated.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.